While I wait for my bearings to arrive so I can really assemble this beast, I decided I would play with how I was going to brace the outside axis rails. At 5′ long there is noticeable deflection with mild pressure applied with one finger. My original intention was to print the 3 pieces and cut conduit to make up the brace but I came up with this as I did not want to spend and other 10 hours printing more parts. I had already printed 4 of the top of the pillar pieces so figured out a way to use them.
I drilled out the hole on top of the printed piece slightly and drilled a hole in to the conduit to accept the 5/16 threaded rod I had left over from the Z Axis. 4 bolts and 7 nylon nuts later this is what I came up with. I has made that rail totally solid.